Method for the production of processed papers



" 3,008,888 1C Patented Nov. 14, 1961 alkali, or a solution of sodium carbonate or trisodium 3,008,888 phosphate may be used. gg% gg gg P g OF The superposed waves used in the invention are formed in such a way that each of said electric waves is oscillated igg g sg ig gaggfiy iggfi ggggggg fi a g 5 separately through, for example, a Colpitts push-pull No nrazvingi Filed June i 1958, set. 724,939 circuit and these circuits are joined into a circuit which Claims priority application Japan July 4 1957 is connected to the electrodes. If the angular frequencies 2 Cl i ((31, 204-165) of the alternating currents thus oscillated are respectively indicated as w; and te the circuit will have an alternat- This invention relates to methods of processing paper ing voltage of the following equation:

and pulp sheets. More particularly, it relates to a method w of producing processed paper in which paper made of eS:\/2E1 Sm cellulose of wood such as red pine (Pinus densiflora), This is not a modulated wave but a voltage in the superbeech (F agus sieboldi), yezo spruce (Pic'ea jezoensis) posed form of alternating currents wi-i-w which is termed and Japanese spruce (Abies sachalinensis) as well as herein as the superposed wave.

J apanese paper is treated with sulfuric acid thereby pro- The following examples are given as illustrations of ducing processed paper which is much improved in waterspecific embodiments of this invention.

resistance and feel and also in strength and especially in E m mple 1 tensile strength, tearing strength and bursting strength.

It is known that parchment paper i produced by treat 0 Three vats contalning sulfuric acid, alkali solution and ing paper with sulfuric acid. Though water-resistant Water respectively afrangedifl alignment 80 that P p and transparent, parchment paper has defects and is easy to be treated may :be passed successively through these to break by bending or tension. Further, known sulfuric vats. The first vat contains sulfuric acid of 55 B. and acid treatment i not applicable to paper made of celthe second alkali vat contains a solution of trisodium lulose of Wood such as red pine, beech and yezo spruce, phosphate of 13 B. in each vat there are provided two since it requires a long time to amyloidize uniformly the metal plates between which the paper is passed. Although surface of such paper, and the paper treated with sulfuric sulphuric acid is a conductor, it has sufiicient resistance acid for a long time is of no practical use due to the fact to avoid short-circuiting the plates. The two plates are that amyloid is deposited deep into the paper thereby connected respectively to two specific current generators deteriorating its strength. provided separately to which medium wave of about Accordingly, an object of the invention is to provide 800-1000 kc. and short wave of about 25-30 me. are an effective method for processing paper made of said applied. wood fibres and pulp sheet and Japanese paper, in which The currents to be supplied by the two generators are the surface of the paper is treated uniformly with sulfuric from about 300 milliamperes to 2 amperes and preferably acid for a very short time to obtain a paper improved about 1 ampere, respectively. The amounts of currents in water-resistance, feel and strength. of the two generators are preferably the same although In accordance with this invention, amyloidation of they may diifer to some extent from each other. The cellulose with sulfuric acid is effected uniformly in a superposed currents flowing in the bath exhibit an excellimited layer at the surface of the paper thereby to prolent effect on the paper under treatment giving good duce paper having not only a soft feel but also improved Water resistance, strength and feel. After the waves are characteristics as particularly regards tensile strength, applied to each bath for about 30 minutes, a paper made tearing strength, bursting strength and Water-resistance. from red pine is passed between said metal plates. When In some cases, the air-permeability is also improved. The p the paper is passed through the sulfuric acid bath in 13 present invention thus provides processed paper most seconds, the treatment time of about 26 seconds is suifisuitable for use as packing or bag paper for cement and cient to accomplish the process including Water-washing. other powder, as well as for sliding-doors and wall-paper. The paper thus treated has a much improved feel and The present invention is characterized in that the treatwater-resistance. ment of paper with sulfuric acid is carried out by pass- The following table shows that the strength and elongaing paper between metal plates to which the superposed tion of the treated paper is remarkably improved over the medium waves and short waves are applied. These 5O untreated paper.

Tensile Breaking Elongation Bursting Strength Strength (kg) Length (km) (percent) Strength ratio leng. cros. long. cros. leng. cros.

Known process: I

Air-dried s. 40 4.32 13.03 10.80 4. 98 4.04 6.4 6.6 Dipped in water for 10 min 6.01 4. 49 7. 8 10. 3 Process of the Invention:

Air-dried 8.91 5.24 16.9 14 5.2 4.35 as 7.2 Dipped in water for 10 min 6. 84 4. 83 8. 4 13. 24

perposed waves may be employed advantageously for f 2 alkali treatment and water-washing. Kraft paper was treated in similar manner as in Ex- For the alkali treatment, a dilute solution of caustic ample l.

The test results of the paper thus treated were as follows:

Treated kraft Kraft paper paper untreated Tensile strength (Normal) (Kg/15 mm.

Wide):

length 6. 1 13. 1 12. 7 crossw 2.6 7. 8. 8 Tensile strength (Wet) (Kg/15 mm. wide):

length 0. 43 6. 2 7. 0 erossw 0. 11 4.0 5. 1 Bursting strength (Normal) (Kg./cm. 1. 6 4.4 4. 9 Bursting strength (Wet) (Kg/cm?) 0 1 and 3. 4 3.0

ess

The above was measured according to JISP 8113 and P 8112.

Temperature at the time of measurement was 30 C. and the humidity 75% RH.

The strength in Wet condition was similarly measured after dipping in water at 30 C. for 30 minutes.

As described above, the processing of paper according to the invention is eifected in a very short time, causing no fear of lowering the strength of the paper but bringing on improvements in strength. Furthermore, this process can be carried out with high efliciency by continuous operation.

The foregoing examples illustrate treatment with sulfuric acid and alkali phosphate, but it is apparent to those skilled in the art that to said treating liquor there may be added penetrants and bufier agents or, in some cases, dyestufis, and that an after-treatment with softener such as glycerine may be added.

What is claimed is:

1. In a method for processing paper by passing it successively through a concentrated sulfuric acid bath, a neutralizing bath containing alkaline compound and a water bath, the improvements comprising the steps of spacing two metallic plates to :form a path therebetween for said paper in said sulfuric acid bath and simultaneously passing between said metallic plates electric currents, one current having a frequency of from 800 to 1000 kc. and the other current having a frequency of from 25 to mc., so that two currents of different frequencies will be superposed.

2. The improvement as claimed in claim 1, wherein the bath of sulfuric acid is maintained at about B. and the alkali bath is a bath of trisodium phosphate at about 13 B.

References Cited in the file of this patent UNITED STATES PATENTS 1,590,595 Hill June 29, 1926 1,791,248 Schwartz Feb. 3, 1931 2,089,966 Kassner Aug. 17, 1937 2,852,452 H'ausner Sept. 16, 1958 

1. IN A METHOD FOR PROCESSING PAPER BY PASSING IT SUCCESSIVELY THROUGH A CONCENTRATED SULFURIC ACID BATH, A NEUTRALIZING BATH CONTAINING ALKALINE COMPOUND AND A WATER BATH, THE IMPROVEMENTS COMPRISING THE STEPS OF SPACING TWO METALLIC PLATES TO FORM A PATH THEREBETWEEN FOR SAID PAPER IN SAID SULFURIC ACID BATH AND SIMULTANEOUSLY PASSING BETWEEN SAID METALLIC PLATES ELECTRIC CURRENTS, ONE CURRENT HAVING A FREQUENCY OF FROM 800 TO 1000 KC. AND THE OTHER CURRENT HAVING A FREQUENCY OF FROM 25 TO 30 MC., SO THAT TWO CURRENTS OF DIFFERENT FREQUENCIES WILL BE SUPERPOSED. 